Monday, December 12, 2011

I got this present in our local radio clubs annual White Elephant Gift Exchange. I think its great! From what I can tell based on the markings, is a 200W power triode that was used in many WW2 radios, and is from about 1943-1945 or so. I am already thinking of a few ham related craft or woodworking projects to use it in.

Saturday, September 17, 2011

I completed building my 440mhz preamp. The main reason I built this was to use for AMSAT reception of the amateur radio satellite downlink signals.

The hardest part with working the satellites is acquiring of the downlink signal from the satellite. That is much harder than the satellite hearing you.

Using a small pre-amp can make a huge difference in being able to establish communications on the satellites.

I chose to build one using the cheap and easy to build kit available from Ramsey Electronics. They have cheap pre-amps for 2m, 220mhz, and 440mhz. Each one is only $14.95. They use a 2SC2498
transistor and provide high gain and very low noise. They have a tuned filter and provide amplification over about 24mhz of bandwidth.

They are popular with the people on the AMSAT mailing list, where they are said to compare favoribly to commercial pre-amps 10-20x the cost. Measurements reported on the mailing list indicate performance of 20db of signal gain, with less than 1db of noise gain.

I chose an old tin box I had to house the finished kit. I save all the tin boxes I can find such as Altoids, and any that come with gifts or whatever. This particular box was from a cartridge that my kids got for the NintendoDS. Its roughly twice the size of an Altoids tin. The size was really needed to house the batteries. In order to keep things simple I used a pair of 9V batteries to power the device. They are wired in series and provide about 18V. Even though the specs say to use 15V, it seems to work just fine with the 16-18V the two 9v batteries in series provide. The twin batteries should provide a long battery life between changes as well.

The first thing I did was to start to mount the external connectors. This consisted of a pair of BNC Jacks, and a SPST switch which will be used for the power ON/OFF.

I have become a fan of using various metal tins for my kits and projects. I have discovered one invaluable tool to use for the metal work is a metal hole punch. I bought a cheap one from Amazon which comes with dies for making various size holes. It works quite well, and makes very neat holes in the tins. I definitely recommend it if your going to be using Altoids tins and similar boxes for any kit building.

Once the external connections were made, I mounted a couple of 9V battery clips inside the box using a bit of JBWeld.

Then I mounted the finished board, and made all the internal wiring connections. The kit board looks small in this box big enough for the two 9V batteries.

Added a some labels from the ole label maker on the cover, and its complete and ready to go. Doing some testing with the amp, its sounds quite good.

I plan on using this with my ARROW Antenna, and maybe velcro mounting somehow to the tripod or something similar. I am also considering adding a LED to the circuit to show the power is on, in order to help visually provide a assistance to try and keep from forgetting to turn it off.

UPDATE:

It is also important to note that since this has no TX/RX switching built in this is for RX use only. I built this primarily to use for working on amateur satellites. In order to use the AMSAT's you transmit on 2m and recieve on 70cm. The Arrow Antenna is actually two separate (2m/70cm) yagi antennas on a single mast, and each antenna has its own feed line connection.

Using a Comet CF-416 diplexer, I connect those antennas to the same radio, or sometimes I actually use two radios and have one for RX and one for TX.. this lets you hear yourself echo on the satellite repeater.

Here is how it would look in a block diagram. Even though the arrow is a single antenna mast, I show it broken out into two separate antennas in this drawing.

Just for reference here are pics of the Arrow Antenna and the Comet CF-416.

The OTHER option for working the satellites is to scrap the diplexer and just use 2 HT's or an HT and a scanner. One HT will be connected to the 2m feed line and used for TX, and the other will be connected to the 70cm feed line and used for RX. The advantage here is you can monitor your signal and listen to yourself bounce off the satellite.

Sunday, September 11, 2011

Some of the states I thought would be hard were easy, and some of the ones I thought would be easy turned out to be more difficult. Just the way it goes I guess. Now its onto 5-band WAS, and I think the ARRL Triple-Play(WAS CW+Digital+SSB) is one I would really like to get.

Monday, August 22, 2011

Based on some discussion on the ft450 owners yahoo group mailing list, this is not a totally uncommon problem. Apparently, Yaesu used some poor quality 3.5mm jacks on this radio, and they are extremely sensitive to the quality of the cable plugged into them.

The issue is that the contacts inside the jacks get easily stuck on any ridges of the plug as it is inserted/removed. Look at any 3 conductor 3.5mm(1/8th in.) plug such as a pair of headphones and notice the construction of the tip, a ring of insulating plastic, another ring for one conductor, a second ring of plastic, and then barrel of the plug.

Run your fingernail along the plug from tip back towards the barrel. Do you feel any ridges or bumps as you pass over the conductors and insulators? What i have found common is that there insulators are where you will find the issue. The insulators will be a slightly different diameter than the metallic parts of the plug, and you will feel the ridges.

On the cheap jacks that Yaesu used, the contacts inside will get hooked on and caught on any of those little ridges or differences in diameter. You will then have to use a great deal of force to pull the plug out, and will bend/break the contacts inside the jack. Eventually, you will find your jack will no longer work or make contact with one or more of the cable conductors. That is what happened to the CW jack on my FT-450, and so the jack needs to be replaced. A word of warning. The headphones jack is the exact same type of jack, as is the speaker out on the back of the radio, so you need to be aware of the same issue for those jacks as well.

The way to ensure that this DOES not happen to you is easy. Make sure that every 3.5mm plug you put into your radio is as smooth as possible and has no ridges or bumps along its length. You will be very surprised at the variation in quality that you will find in this regard once you start checking them. A recommendation that I got from the yaesu mailing list, that I am using myself is to purchase a RadioShack 3.5mm Y-cable, and plug that into the jack first, and then plug whatever cw key, headphones etc, you want into that pigtail. For whatever reason the plug on the radio shack Y-cable is very smooth and makes an excellent friend to to the FT-450 jacks. I can't find the product on their website, but its in the store with all the other radio shack extension cables, adapters, etc. Is their cheap black 3.5mm(1/8inch) Y-splitter cable, not the fancy gold colored one or a name brand one, the cheapo radio shack version.

I tried to document what I did as much as possible to share with others who want to undertake this operation on their radio.

As it turns out my warranty expired a few months ago, and since I have already been inside butchering my radio to make a modification for SDR use a while back, I figured instead of sending it back to Yaesu to pay the service charge and shipping to-and-fro for the repair, I would give this repair a go as well in my quest to be more than an 'appliance user' ham. Barely a year having a new $900 radio, and I have been inside with the soldering iron a dozen times or so, so I guess I am off to a start.

The part number for the replacement jacks from Yaseu is P1091426. They are only a couple of dollars for a pair of them. I ordered two so I would have an extra in case I messed up somehow. Or for when the next one fails, *sigh*. They do seem to be a little different than the original ones, so hopefully they are using a slightly better quality part than the original and will last longer. Of course, now I know how to baby the FT-450 jacks and that should help make them last longer as well.

First thing on the list is disassembly of the FT-450. Like I said, I am already an old pro at this from my other mods. Its actually quite easy to get to the inside of the FT-450.

There are 4 screws on the top cover to remove, and four identical on the bottom as well(don't remove the rubber feet screws).:

Then there are 4 screws to remove on each side:

Now we can slide back the top and bottom covers. We don't actually need to take the covers off the radio for this work, so I just slid them back a bit from the front to provide access to the panel.

To remove the front panel you have to slide those plastic tabs over the screw holes, there are two tabs on the top and another set of the bottom.

Once you have all 4 plastic tabs from the top and bottom of the front panel clear of the screw holes, you can slide the front panel all the way off the radio:

The front panel is disconnected from the radio by removing that small ribbon cable from the jack on the PCB. But FIRST, make some marks on the cable to make sure you can remember the exact orientation of the cable to put it back together.

I used a sharpie marker to make a mark on the same side of the cable and the plug, then I just have to line them up when putting it back together.

To remove the cable, pull carefully, and it will come out. Some cables like this have little tabs to pull up on the socket that loosen the cable, but this one does not. The cable is just held in by friction.

Now we have the front panel free from the radio and move it to a work surface and put the base of the radio out of the way.

Next we start to disassemble the front panel to get full access to both sides of the PCB. Remove the 4 smaller knobs(shift,dsp,rf,af) as shown above, they are held on only by friction. The main tuning know is held on by a small set screw. First you have to remove the rubber grip ring around the tuning knob to get access to the set screw.

The set screw is removed using a small 2-mm (5/64”) allen wrench to loosen this screw.

Once the screw is loosened, you can remove the main tuning knob. Remove the tension spring and plastic washer from the main dial screw and set those parts aside.

Then remove all of the nuts and washers from the four smaller knobs using a 10mm socket. I used a deep well socket to make it easier. Set those nuts and washers aside for safe keeping.

Turn the panel over to the back of the PCB.

Remove the screws from the back of the PCB that hold it to the front panel plastic. Look for the screws with the rings around them like these:

Disconnect the cable that connects the PCB to the main tuning knob. Write down the colors, take a picture like this, or make a sharpie mark like I did for the ribbon cable to help you make sure assembly goes easy.

Now the PCB can be removed from the front panel and put onto a work surface.

We will be replacing the bottom 3.5mm jack(cw) on the panel.

Luckily we are not talking about any SMT work here, the jack is a simply through-hole mount. We just have to remove the solder from the posts on the jack to and remove it. There are 6 through-hold conductors on the jack(yellow highlights), and two plastic tabs(purple) that hold it in. Using a solder sucker, solder wick etc to get the solder off as best you can. I also ended up chewing up the jack from the front to get to the leads and snipping them off the jack, and then used the solder suck to clean the holes out. You can see I pretty much destroyed the old jack with my wire cutters.

After I you get the jack off, make sure the holes and the PCB are as clean as possible. Notice my destructive work on the jack from the front caused a couple of light scratches on the front of the PCB. Nothing was really harmed and these ended up being just cosmetic, but there are some traces hidden there under the jack and you should probably try and be more careful than I was. The PCB is easy to scratch, so be gentle with it, and yours will most likely come out a little neater looking than mine.

So, now that we have the old jack out and the holes clean, we can put the new jack in and solder it into place. Notice the new jack has black tabs instead of white ones like the old jack.

After cleaning the PCB with some alcohol to remove the flux residue from the soldering, its an almost good as new.

I connected the ribbon cable to the radio, powered it on and did a quick test of my CW jack and it works! Repair successful, now its time for reassembly.

The assembly is just the same as doing the disassemble, just in reverse. One thing I did is when I ordered the replacement 3.5mm jacks from Yaesu, I also ordered the new FT-450D style replacement dial kit which I will be putting on during re-assembly. Yaesu Part#s RA082910B(knob) and RA0829300(rubber ring). Click Here for More Info. Here they are side-by-side to see the difference.

The new tuning knob is much beefier, and heavier, and it protrudes from the radio a bit more making it easier to tune with the larger surface area for the fingers. To install the new style knob, you leave off the tension spring and the plastic washer and just put the knob all the way on the tuning shaft and tighten the set screw.

Once re-assembly tip is to make sure you use a lint-free micro-fiber cleaning cloth to clean off the clear inside plastic of the panel where the display is, and to wipe off the display panel as well to make sure you do not get any fingerprints, or dust trapped 'permanantly' inside the radio display.

And there you have it. All back together and ready for action. Repair successful. Time and money saved, a little more electronics repair experience.

Friday, July 29, 2011

I wanted to take a few minutes to document the construction of the grounding system for my station which I did a few years ago. This is an often confusing item for newer hams and maybe this will give some ideas that can be used or expanded on by someone else.

The basic design consists of a weather sealed single point box, that all the EMP/lightning arrestors are installed into, and all the antennas come in through that box connected to an arrestor. That box has a ground connection that goes into the shack for a single ground bus inside for connecting the antenna switches and for other inside grounding connections.

I used an aluminum NEMA style weather proof box I was able to find cheap as surplus, to mount all my arrestors. A single ICE HF arrestor is shown in the photo, there is a second ICE Arrestor for VHF, and a Polyphaser HF arrestor mounted in there today. You can see the 2" copper strap was attached directly to the aluminum panel inside the box, and the arrestors are screwed into the box on top of the copper. The copper is polished first using a scotchbrite, and then the arrestors are mounted using coatings of Anti-Oxidant such as that available from IDEAL Industries. This will help ensure a long life electrical connection between the parts.

For the COAX, holes were drilled into the sides, and weatherproof coax connectors were used to seal the coax passthroughs. They worked very well, and are available from DX engineering.

The box is mounted on a PVC pipe put into the soil under the window that leads to the shack which suspends it a few feet off the ground. A ground rod is in the ground just in front and under the single point ground box. The copper strap from the single point box connects to the ground rod underneath it, and an additional copper strap goes through the window into the shack to connect to a grounding bus on the inside.

On the inside, the copper strap passing through the window is mounted to a board that has another copper strap attached to create a grounding bus for things like antenna switches, tuners etc. This photo shows the board sitting on a small desk, but now This board is now mounted to the wall directly under the window with more switches added to it. (You can see a peek of it in one of the photos of the FT-450 Jack Repair Page).

From the main ground rod just below the single point ground NEMA box, there is grounding strap run underground to several other ground rods in a radial pattern at more than 8 feet apart in every direction.

For the other ground rods, a string was pulled to them to make a straight guide line, and then a trench was made for the copper strap a by just wiggling a hand spade/shovel to allow for putting the strap a few inches under the ground.

This was repeated to several more ground rods.

For each one I used a mechanical connection between the copper straps and the ground rods. A good physical clamping connection is the easiest and pretty reliable using the sort of clamps I used which are made for clamping strap, and again the process of polishing all the copper surfaces and coating them with anti-ox before making the mechanical connections was used.

This photo shows the flat clamps used for the strap, and a single wire clamp used for a the #4 wire that was connected to the interior electrical breaker panel.

Since I didn't have enough of the custom strap clamps for all the ground rods, on one of the strap-to-rod connections I used another connection method that someone suggested. It involves forming a tube on the end of the strap and placing over the top of the rod, and then mechanically clamping it into place. This method actually worked pretty well, so if you don't want to spend the money on the strap clamp which are a little expensive, I think that it might be a good way to connect your system. Again, use the same process of polishing all copper surfaces to remove oxidation, and coat with anti-ox compounds before clamping together.

At the ground rod closest to the side towards where the electrical panel is located, a #4 gauge wire was run from the ground rod to the ground bus in the interior electrical breaker panel. This ensures that all ground connections are bonded together and at equal potential. This is an often overlooked step, and is in fact required by national electrical codes(NEC).

When all was completed, I ended up with a fairly decent grounding system for a home radio station, consisting of 5 ground rods all connected to a single point grounding entrance panel.